The purpose is to investigate the abilities of deaf persons to perceive various qualities of complex auditory stimuli, especially those qualities that are important in speech perception. The method is to compare abnormal and normal audition using tests of discrimination and identification of specially designed sound stimuli having known acoustical characteristics. The comparisons are made so as to develop new psychoacoustic information on the perceptual effects of sensorineural pathologies of audition. Discrimination and identification measures are carried out for known timbre differences among vowel sounds, simulated consonant sounds, and sound spectral patterns which vary in time, such as format transitions.